The woven product is to be used in a paper machine, that is in a machine for production of paper/paper pulp. The felt is placed in a given roller group in the paper machine. The tubular felt is in the form of a hose, the circumference of which is adapted in the weaving machine to the roller group in the paper machine in which it is to run. When the woven felt is mounted in the paper machine, the side walls of the machine are dismantled so that the ends of the rollers are freed and the woven felt can then be pushed in over the roller group. To produce the tubular felts, a weaving machine is required, which has a working width corresponding to half the circumference of the felt. As a roller group in the paper machine may have a large circumference, the working width of the weaving machine becomes considerable and working widths of roughly 30 meters may be cited by way of example. Production of tubular felt is a difficult process as there are in principle two felts which lie loosely one on top of the other in the weaving machine, which may give rise to problems.
It is previously known use cloth beam arrangements with three beams. The feed of the arrangement is adjusted in such a manner that each time a shuttle passes across the width of the weaving machine, the beam system is rotated forward by a given amount which is to correspond to the thread pitch in the felt. Reference may also be made to the current system sold on the open market by TEXO AB. The system is described in, for example, Swedish patent 8703865. In this known system. all are gearwheel-synchronized and the beams are advanced by the same distance. In so-called flat-woven products with only one felt ply, the known system functions excellently.
In the weaving of the tubular felts with an overfelt and an underfelt, problems arise when the known cloth beam arrangement is used. This is because the overfelt and the underfelt can be displaced in relation to one another. As is described in greater detail below, the underfelt and the overfelt have different driving radii in the cloth beam arrangement. During advance of the cloth beams, the overfelt is moved a slightly greater distance than the underfelt as a result of the radius of movement being longer for the overfelt than for the underfelt. This has such an effect that a noticeable displacement occurs between the two felt plies at the weaving edge or beating-up edge. This means that differences arise in the sett of the two felts. The underfelt, which by means of the cloth beam arrangement has the correct adjustment, has the expected sett while the overfelt has a looser sett. This has consequences in the paper machine in connection with paper production because the tubular felt has a sett which varies around its circumference. The invention aims to solve this problem.
It is important that the identical feed of the overfelt and the underfelt during weaving can take place irrespective of the felt thickness in the woven material. The cloth beam system/weaving machine is thus to be adjustable for different felt thicknesses and still effect the desired felt feed in the case of tubular felts. The invention solves this problem also.
The main characterizing feature of the new arrangement is considered to be use of driving members which bring about driving of the beams which prevents mutual longitudinal displacement movements between the overfelt and the underfelt and thus ensures during weaving that the overfelt and underfelt edges remain opposite one another at the weaving edge(s). The term opposite means that the overfelt and the underfelt are to cover or overlap one another (completely) at the weaving edge or weaving edges respectively.
In developments of the inventive idea, the driving members are designed to effect an unsynchronized rotation of at least the first and second beams. The driving members may comprise, for the first beam or upper beam, first driving members which drive the first beam via its two ends by means of first a.c. servo-motors. The first beam is in this connection designed freely programmable with regard to the sett in the woven material.
In a further embodiment, the second beam or intermediate beam is assigned second driving members which drive the second beam at a reduced speed of rotation in relation to the third beam. The second and third beams may form part of a common driving assembly which is driven by second driving members via the two ends of each beam of the second and third beams. The second driving members may comprise gearwheels mechanically interconnecting the second and third beams. The gearwheels bring about, by means of synchronization, a slightly higher driving speed of the third beam in relation to the second beam, resulting in a desired tensile stress being maintained in the overfelt. The second and third beams which form the common driving assembly can be driven by means of second a.c. servo-motors arranged at the two ends of the driving assembly (or of the beams). The overdriving of the third beam in relation to the second beam is brought about by the gearwheel of the third beam having fewer teeth than the gearwheel of the second beam.
In a further embodiment, the driving members are designed to drive the three beams in an entirely unsynchronized manner so that there is complete programming freedom for the drive functions of the beams.
The a.c. servo-motors mentioned above may, in a known manner, be made controllable from a unit, which controls the weaving, on or close to the machine.
By means of the above proposals, the process of weaving tubular felts in a weaving machine is made easier and the sley or reed can attack a common edge of the woven felt plies, which guarantees a uniform sett around the entire circumference of the tubular felt. By the beams different speeds, the feed of the overfelt and the underfelt can be coordinated in an entirely different manner from that which has been possible previously using the known equipment. The feed is also independent of the thickness of the woven material. Differences in radius which give rise to the felt displacement are compensated by differences in speed of the beams which have essentially the same diameter.